Rising CO2 Levels in Water Brings Risk to Entire Marine Food Chain

Escalating carbon dioxide emissions will cause fish to lose their fear of predators, potentially damaging the entire marine food chain, joint Australian and US research has found.

A study by the Australian Institute of Marine Science, James Cook University and the Georgia Institute of Technology found the behavior of fish would be “seriously affected” by greater exposure to CO2.

They found that fish living near the vents, where bubbles of CO2 seeped into the water, “were attracted to predator odour, did not distinguish between odours of different habitats, and exhibited bolder behaviour than fish from control reefs”.

The gung-ho nature of CO2-affected fish means that more of them are picked off by predators than is normally the case, raising potentially worrying possibilities in a scenario of rising carbon emissions.

More than 90% of the excess CO2 in the atmosphere is soaked up by the oceans. When CO2 is dissolved in water, it causes ocean acidification, which slightly lowers the pH of the water and changes its chemistry. Crustaceans can find it hard to form shells in highly acidic water, while corals risk episodes of bleaching.